Four foodborne disease outbreaks caused by a new type of enterotoxin-producing Clostridium perfringens

Binary Enterotoxin Producing Clostridium perfringens Isolated in Blood Cultures: Case Report and Review of the Literature

Clostridium perfringens (C. perfringens) is an anaerobic, spore-forming Gram-positive rod responsible for necrotizing gangrene, bacteremia in patients with cancer or gastrointestinal tract infection. C. perfringens virulence is due in large part to toxin production. In 2014, a new enterotoxin, BEC (binary enterotoxin of Clostridium perfringens) encoded by becA and becB genes, distinct from enterotoxin (CPE) encoded by the cpe gene, has been described. BEC-producing strains can be causative agents of acute gastroenteritis in humans. We present herein the case of a 64-year-old man who presented to the emergency department of Toulouse University Hospital with pneumonia and septic shock, without digestive symptoms. Blood cultures showed C. perfringens bacteremia and despite appropriate antibiotic treatment the patient passed away 7 h after admission. The characterization of the strain by whole genome sequencing revealed the presence of typical genes of C. perfringens: plc gene (alpha-toxin, phospholipase C) and pfoA (theta-toxin, perfringolysine). Surprisingly, this strain also harbored becA and becB genes encoding the recently described BEC toxin. Interestingly, alpha-toxin typing of our isolate and other published BEC isolates showed that they belonged to different PLC subtypes, confirming the high genetic diversity of these strains. To our knowledge, it is the first clinical case reporting bacteremia due to a BEC-producing C. perfringens isolate.

Usefulness and Limitations of PFGE Diagnosis and Nucleotide Sequencing Method in the Analysis of Food Poisoning Pathogens Found in Cooking Employees

In the case of a food poisoning outbreak, it is essential to understand the relationship between cooking workers and food poisoning. Many biological diagnostic methods have recently been developed to detect food poisoning pathogens. Among these diagnostic tools, this study presents PCR-based pulsed-field gel electrophoresis and nucleotide sequencing diagnostic analysis results for diagnosing food poisoning outbreaks associated with cooking employees in Chungcheongnam-do, Republic of Korea. Pulsed-field gel electrophoresis was useful in identifying the food poisoning outbreaks caused by Staphylococcus aureus and Enteropathogenic Escherichia coli. In the case of Norovirus, nucleotide sequencing was used to identify the relationship between cooking workers and the food poisoning outbreak. However, it is difficult to determine whether cooking employees directly caused the food poisoning outbreaks based on these molecular biological diagnostic results alone. A system is needed to integrate epidemiological and diagnostic information to identify a direct correlation between the food poisoning outbreak and cooking employees.

Characterization of G-type Clostridium perfringens bacteriophages and their disinfection effect on chicken meat

OBJECTIVE

Clostridium perfringens is one of most important bacterial pathogens in the poultry industry and mainly causes necrotizing enteritis (NE). This pathogen and its toxins can cause foodborne diseases in humans through the food chain. In China, with the rise of antibiotic resistance and the banning of antibiotic growth promoters (AGPs) in poultry farming, food contamination and NE are becoming more prevalent. Bacteriophages are a viable technique to control C. perfringens as an alternative to antibiotics. We isolated Clostridium phage from the environment, providing a new method for the prevention of NE and C. perfringens contamination in meat.

METHODS

In this study, we selected C. perfringens strains from various regions and animal sources in China for phage isolation. The biological characteristics of Clostridium phage were studied in terms of host range, MOI, one-step curve, temperature and pH stability. We sequenced and annotated the genome of the Clostridium phage and performed phylogenetic and pangenomic analyses. Finally, we studied its antibacterial activity against bacterial culture and its disinfection effect against C. perfringens in meat.

RESULTS

A Clostridium phage, named ZWPH-P21 (P21), was isolated from chicken farm sewage in Jiangsu, China. P21 has been shown to specifically lyse C. perfringens type G. Further analysis of basic biological characteristics showed that P21 was stable under the conditions of pH 4-11 and temperature 4-60 °C, and the optimal multiple severity of infection (MOI) was 0.1. In addition, P21 could form a "halo" on agar plates, suggesting that the phage may encode depolymerase. Genome sequence analysis showed that P21 was the most closely related to Clostridium phage CPAS-15 belonging to the Myoviridae family, with a recognition rate of 97.24% and a query coverage rate of 98%. No virulence factors or drug resistance genes were found in P21. P21 showed promising antibacterial activity in vitro and in chicken disinfection experiments. In conclusion, P21 has the potential to be used for preventing and controlling C. perfringens in chicken food production.

Inactivation of Clostridium perfringens C1 Spores by the Combination of Mild Heat and Lactic Acid

Clostridium perfringens is a major pathogen causing foodborne illnesses. In this experiment, the inactivation effects of heat and lactic acid (LA) treatments on C. perfringens spores was investigated. Heat treatment (80 °C, 90 °C and 100 °C), LA (0.5% and 1%), and combined LA and heat treatments for 30 and 60 min were performed. Residual spore counts showed that the count of C. perfringens spores was below the detection limit within 30 min of treatment with 1% LA and heat treatment at 90 °C. Scanning electron microscopy and confocal scanning laser microscopy results showed that the surface morphology of the spores was severely disrupted by the co-treatment. The particle size of the spores was reduced to 202 nm and the zeta potential to −3.66 mv. The inner core of the spores was disrupted and the co-treatment resulted in the release of 77% of the nuclear contents 2,6-pyridinedicarboxylic acid. In addition, the hydrophobicity of spores was as low as 11% after co-treatment with LA relative to the control, indicating that the outer layer of spores was severely disrupted. Thus, synergistic heating and LA treatment were effective in inactivating C. perfringens spores.

Characterization and optimization of bacteriophage cocktails to control Clostridium perfringens in vitro and in curry roux

Clostridium perfringens is a major cause of foodborne disease in developed countries. The aim of this study was to isolate and characterize phages specific to C. perfringens to evaluate the most efficient phage cocktail for the biocontrol of C. perfringens, both in vitro and in curry roux. In this study, four phages were isolated from chicken meat and were morphologically and genetically characterized along with two phages previously isolated in our laboratory that display different host lysis spectra. Phage cocktail CP11, consisting of phages CPQ3, 7, 8, and 10, showed the broadest host range. Electron micrograph images suggested that all four phages belong to the Podoviridae family, and none of them carry any antibiotic resistance or toxin genes. Notably, the phages were stable at various pH values and in curry roux. Cocktails consisting of six, five, and four phages at the same concentrations were examined to determine the most effective phage cocktail. Phage cocktail PC11 significantly decreased the viable count of C. perfringens to a value less than the lower detection limit up to 48 h at both 8 and 37 °C in broth and at 24 °C in the curry roux. These results suggest that phage cocktail PC11 is a promising natural biocontrol agent against C. perfringens in vitro and in curry roux.

Analysis of the complete genome sequences of Clostridium perfringens strains harbouring the binary enterotoxin BEC gene and comparative genomics of pCP13-like family plasmids

Background

BEC-producing Clostridium perfringens is a causative agent of foodborne gastroenteritis. It was first reported in 2014, and since then, several isolates have been identified in Japan and the United Kingdom. The novel binary ADP-ribosylating toxin BEC, which consists of two components (BECa and BECb), is encoded on a plasmid that is similar to pCP13 and harbours a conjugation locus, called Pcp, encoding homologous proteins of the type 4 secretion system. Despite the high in vitro conjugation frequency of pCP13, its dissemination and that of related plasmids, including bec-harbouring plasmids, in the natural environment have not been characterised. This lack of knowledge has limited our understanding of the genomic epidemiology of bec-harbouring C. perfringens strains.

Results

In this study, we determined the complete genome sequences of five bec-harbouring C. perfringens strains isolated from 2009 to 2019. Each isolate contains a ~ 3.36 Mbp chromosome and 1–3 plasmids of either the pCW3-like family, pCP13-like family, or an unknown family, and the bec-encoding region in all five isolates was located on a ~ 54 kbp pCP13-like plasmid. Phylogenetic and SNP analyses of these complete genome sequences and the 211 assembled C. perfringens genomes in GenBank showed that although these bec-harbouring strains were split into two phylogenetic clades, the sequences of the bec-encoding plasmids were nearly identical (>99.81%), with a significantly smaller SNP accumulation rate than that of their chromosomes. Given that the Pcp locus is conserved in these pCP13-like plasmids, we propose a mechanism in which the plasmids were disseminated by horizontal gene transfer. Data mining showed that strains carrying pCP13-like family plasmids were unexpectedly common (58/216 strains) and widely disseminated among the various C. perfringens clades. Although these plasmids possess a conserved Pcp locus, their ‘accessory regions’ can accommodate a wide variety of genes, including virulence-associated genes, such as becA/becB and cbp2. These results suggest that this family of plasmids can integrate various foreign genes and is transmissible among C. perfringens strains.

Conclusion

This study demonstrates the potential significance of pCP13-like plasmids, including bec-encoding plasmids, for the characterisation and monitoring of the dissemination of pathogenic C. perfringens strains.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08453-4.

Characterization of Clostridium perfringens bacteriophages and their application in chicken meat and milk

Clostridium perfringens is one of the most important foodborne pathogens in developed countries. It causes severe food poisoning outbreaks worldwide, along with mortality and economic losses. Recently, bacteriophages have been investigated as an alternative tool to control pathogenic bacteria in the food industry. In this study, 19 Clostridium perfringens and 6 Clostridium perfringens bacteriophages were isolated from chicken meat. According to host range and stability tests, bacteriophage CPQ1 showed high thermostability and the broadest host range. The electron micrograph image of this bacteriophage suggested that it belongs to the Picovirinae subfamily of the Podoviridae family. Nucleotide sequence analysis of the genomic DNA indicated the absence of any antibiotic resistance, toxin, or virulence genes. In broth, CPQ1 showed strong lytic activity with a low MOI of 1, decreasing the OD₆₀₀ of Clostridium perfringens cell suspension from 0.2 to 0.02 at 37 °C in 2 h. In pasteurized milk and chicken meat, CPQ1 with an MOI of 10 also caused a significant decrease in viable counts of Clostridium perfringens compared to the bacteriophageless control at both 24 °C and 37 °C. This is the first report on the application of bacteriophage to control Clostridium perfringens in foods.

Clonal diversity of Clostridium perfringens human clinical isolates with various toxin gene profiles based on multilocus sequence typing and alpha-toxin (PLC) typing

OBJECTIVES

Clostridium perfringens is a common anaerobic pathogen causing enteritis/enterocolitis and wound infections in humans. We analyzed clonal diversity and toxin gene prevalence in C. perfringens clinical isolates from humans in northern Japan.

METHODS

Prevalence of nine toxin genes was analyzed for 585 C. perfringens isolates from patients collected for 20-month period between May 2019 and December 2020 by molecular methods. Sequence type (ST) based on multilocus sequence typing (Xiao's scheme) and alpha-toxin (PLC) sequence type were determined for a total of 124 isolates selected in the present study along with those in our previous study (2017-2018).

RESULTS

Toxinotypes A (68.2%) was the most frequent, followed by F (31.6%), and G (0.2%), while additional toxin genes encoding binary enterotoxin (BEC/CPILE) and beta2 toxin were identified in one and six isolates, respectively. Among the 124 isolates with various toxin gene profiles, 62 STs including 53 novel types were identified, revealing the presence of six clonal complexes (CCs) consisting of 27 STs. Most of enterotoxin gene (cpe)-positive isolates belonged to CC36, CC41, and CC117. Based on 22 key amino acids in alpha toxin sequence, four PLC types (I-IV) including 21 subtypes were classified, and their relation to individual STs/CCs was clarified. Two isolates harboring bec/cpile belonged to different STs (ST95, ST131) and PLC types (If, IVb), indicating distribution of this toxin gene to distinct lineages.

CONCLUSIONS

The present study revealed the diversity in C. perfringens clones of human origin with various toxin gene profiles represented by ST/CC and PLC type.

Clostridium perfringens as Foodborne Pathogen in Broiler Production: Pathophysiology and Potential Strategies for Controlling Necrotic Enteritis

Clostridium perfringens (Cp.) is the cause of human foodborne desease. Meat and poultry products are identified as the main source of infection for humans. Cp. can be found in poultry litter, feces, soil, dust, and healthy birds' intestinal contents. Cp. strains are known to secrete over 20 identified toxins and enzymes that could potentially be the principal virulence factors, capable of degrading mucin, affecting enterocytes, and the small intestine epithelium, involved in necrotic enteritis (NE) pathophysiology, also leading to immunological responses, microbiota modification and anatomical changes. Different environmental and dietary factors can determine the colonization of this microorganism. It has been observed that the incidence of Cp-associated to NE in broilers has increased in countries that have stopped using antibiotic growth promoters. Since the banning of such antibiotic growth promoters, several strategies for Cp. control have been proposed, including dietary modifications, probiotics, prebiotics, synbiotics, phytogenics, organic acids, and vaccines. However, there are aspects of the pathology that still need to be clarified to establish better actions to control and prevention. This paper reviews the current knowledge about Cp. as foodborne pathogen, the pathophysiology of NE, and recent findings on potential strategies for its control.

Diagnostic Accuracy of Nucleic Acid Amplification-Based Assays for Clostridium perfringens-Associated Diseases: a Systematic Review and Meta-analysis

Timely and accurate methods for detecting Clostridium perfringens-associated diseases (CPAD) are crucial to improve patient care. A number of studies have evaluated the accuracy of nucleic acid amplification tests (NAAT) in detecting CPAD, but decisive results about their effectiveness have not been reported. We conducted a meta-analysis to evaluate the diagnostic performance of NAAT for detecting C. perfringens in clinical diarrheal samples. Five databases including PubMed, Embase, Scopus, Web of Science, and the Cochrane library were systematically probed for studies published before 6 December 2019. From 2,632 citations, we identified five eligible studies comprising 817 samples. Three studies (n = 695 samples) compared NAAT with a microbiological culture while the other three studies (n = 322 samples) compared NAAT with an immunoassay. NAAT revealed higher diagnostic accuracy against immunoassay (sensitivity, 0.53 [95% confidence interval [CI], 0.35 to 0.7]; specificity, 0.97 [95% CI, 0.95 to 0.99]; positive likelihood ratio [PLR], 23.2 [95% CI, 3.49 to 153.98]; negative likelihood ratio [NLR], 0.25 [95% CI, 0 to 245.28]; diagnostic odds ratio [DOR], 74.11 [95% CI, 2.11 to 2,593.7]) than microbiological culture (sensitivity, 0.31 [95% CI, 0.22 to 0.41]; specificity, 0.95 [95% CI, 0.93 to 0.97]; PLR, 11.56 [95% CI, 3.87 to 34.6]; NLR, 0.57 [95% CI, 0.27 to 1.21]; DOR, 18.1 [95% CI, 4.83 to 67.8]). NAAT pooled specificity was consistently ≥95% against that of applied reference standards. A meta-regression and subgroup analysis of sample condition, gene target, study design, and reference standards could not explain the heterogeneity (P > 0.05) in the diagnostic efficiency. The analysis has demonstrated that the diagnostic accuracy of NAAT is relatively insufficient to replace traditional reference standards as a single diagnostic test. NAAT can be applied in combination with microbiological culture because of the advantage of time to result and in scenarios where traditional tests are not feasible. Further investigations in this direction with larger sample sizes are still warranted to support our findings.

Cryo-EM structures reveal translocational unfolding in the clostridial binary iota toxin complex

The iota toxin produced by Clostridium perfringens type E is a binary toxin comprising two independent polypeptides: Ia, an ADP-ribosyltransferase, and Ib, which is involved in cell binding and translocation of Ia across the cell membrane. Here we report cryo-EM structures of the translocation channel Ib-pore and its complex with Ia. The high-resolution Ib-pore structure demonstrates a similar structural framework to that of the catalytic ϕ-clamp of the anthrax protective antigen pore. However, the Ia-bound Ib-pore structure shows a unique binding mode of Ia: one Ia binds to the Ib-pore, and the Ia amino-terminal domain forms multiple weak interactions with two additional Ib-pore constriction sites. Furthermore, Ib-binding induces tilting and partial unfolding of the Ia N-terminal α-helix, permitting its extension to the ϕ-clamp gate. This new mechanism of N-terminal unfolding is crucial for protein translocation.

Clostridial Binary Toxins: Basic Understandings that Include Cell Surface Binding and an Internal "Coup de Grâce"

Clostridium species can make a remarkable number of different protein toxins, causing many diverse diseases in humans and animals. The binary toxins of Clostridium botulinum, C. difficile, C. perfringens, and C. spiroforme are one group of enteric-acting toxins that attack the actin cytoskeleton of various cell types. These enterotoxins consist of A (enzymatic) and B (cell binding/membrane translocation) components that assemble on the targeted cell surface or in solution, forming a multimeric complex. Once translocated into the cytosol via endosomal trafficking and acidification, the A component dismantles the filamentous actin-based cytoskeleton via mono-ADP-ribosylation of globular actin. Knowledge of cell surface receptors and how these usurped, host-derived molecules facilitate intoxication can lead to novel ways of defending against these clostridial binary toxins. A molecular-based understanding of the various steps involved in toxin internalization can also unveil therapeutic intervention points that stop the intoxication process. Furthermore, using these bacterial proteins as medicinal shuttle systems into cells provides intriguing possibilities in the future. The pertinent past and state-of-the-art present, regarding clostridial binary toxins, will be evident in this chapter.

Prevalence and Genetic Diversity of Toxin Genes in Clinical Isolates of Clostridium perfringens: Coexistence of Alpha-Toxin Variant and Binary Enterotoxin Genes (bec/cpile)

Clostridium perfringens (C. perfringens) is responsible for food-borne gastroenteritis and other infectious diseases, and toxins produced by this bacterium play a key role in pathogenesis. Although various toxins have been described for C. perfringens isolates from humans and animals, prevalence of individual toxins among clinical isolates has not yet been well explored. In the present study, a total of 798 C. perfringens clinical isolates were investigated for prevalence of eight toxin genes and their genetic diversity by PCR, nucleotide sequencing, and phylogenetic analysis. Besides the alpha-toxin gene (plc) present in all the isolates, the most common toxin gene was cpe (enterotoxin) (34.2%), followed by cpb2 (beta2 toxin) (1.4%), netB (NetB) (0.3%), and bec/cpile (binary enterotoxin BEC/CPILE) (0.1%), while beta-, epsilon-, and iota-toxin genes were not detected. Genetic analysis of toxin genes indicated a high level of conservation of plc, cpe, and netB. In contrast, cpb2 was revealed to be considerably divergent, containing at least two lineages. Alpha-toxin among 46 isolates was classified into ten sequence types, among which common types were distinct from those reported for avian isolates. A single isolate with bec/cpile harbored a plc variant containing an insertion of 834-bp sequence, suggesting its putative origin from chickens.

Comparative Studies of Actin- and Rho-Specific ADP-Ribosylating Toxins: Insight from Structural Biology

Mono-ADP-ribosylation is a major post-translational modification performed by bacterial toxins, which transfer an ADP-ribose moiety to a substrate acceptor residue. Actin- and Rho-specific ADP-ribosylating toxins (ARTs) are typical ARTs known to have very similar tertiary structures but totally different targets. Actin-specific ARTs are the A components of binary toxins, ADP-ribosylate actin at Arg177, leading to the depolymerization of the actin cytoskeleton. On the other hand, C3-like exoenzymes are Rho-specific ARTs, ADP-ribosylate Rho GTPases at Asn41, exerting an indirect effect on the actin cytoskeleton. This review focuses on the differences and similarities of actin- and Rho-specific ARTs, especially with respect to their substrate recognition and cell entry mechanisms, based on structural studies.

Crystal structure and structure-based mutagenesis of actin-specific ADP-ribosylating toxin CPILE-a as novel enterotoxin

Unusual outbreaks of food poisoning in Japan were reported in which Clostridium perfringens was strongly suspected to be the cause based on epidemiological information and fingerprinting of isolates. The isolated strains lack the typical C. perfringens enterotoxin (CPE) but secrete a new enterotoxin consisting of two components: C. perfringens iota-like enterotoxin-a (CPILE-a), which acts as an enzymatic ADP-ribosyltransferase, and CPILE-b, a membrane binding component. Here we present the crystal structures of apo-CPILE-a, NAD+-CPILE-a and NADH-CPILE-a. Though CPILE-a structure has high similarity with known iota toxin-a (Ia) with NAD+, it possesses two extra-long protruding loops from G262-S269 and E402-K408 that are distinct from Ia. Based on the Ia-actin complex structure, we focused on actin-binding interface regions (I-V) including two protruding loops (PT) and examined how mutations in these regions affect the ADP-ribosylation activity of CPILE-a. Though some site-directed mutagenesis studies have already been conducted on the actin binding site of Ia, in the present study, mutagenesis studies were conducted against both α- and β/γ-actin in CPILE-a and Ia. Interestingly, CPILE-a ADP-ribosylates both α- and β/γ-actin, but its sensitivity towards β/γ-actin is 36% compared with α-actin. Our results contrast to that only C2-I ADP-ribosylates β/γ-actin. We also showed that PT-I and two convex-concave interactions in CPILE-a are important for actin binding. The current study is the first detailed analysis of site-directed mutagenesis in the actin binding region of Ia and CPILE-a against both α- and β/γ-actin.

Identification and Characterization of a New Enterotoxin Produced by Clostridium perfringens Isolated from Food Poisoning Outbreaks

There is a strain of Clostridium perfringens, W5052, which does not produce a known enterotoxin. We herein report that the strain W5052 expressed a homologue of the iota-like toxin components sa and sb of C. spiroforme, named Clostridium perfringens iota-like enterotoxin, CPILE-a and CPILE-b, respectively, based on the results of a genome sequencing analysis and a systematic protein screening. In the nicotinamide glyco-hydrolase (NADase) assay the hydrolysis activity was dose-dependently increased by the concentration of rCPILE-a, as judged by the mass spectrometry analysis. In addition, the actin monomer of the lysates of Vero and L929 cells were radiolabeled in the presence of ^[32P]NAD and rCPILE-a. These findings indicated that CPILE-a possesses ADP-ribosylation activity. The culture supernatant of W5052 facilitated the rounding and killing of Vero and L929 cells, but the rCPILE-a or a non-proteolyzed rCPILE-b did not. However, a trypsin-treated rCPILE-b did. Moreover, a mixture of rCPILE-a and the trypsin-treated rCPILE-b enhanced the cell rounding and killing activities, compared with that induced by the trypsin-treated rCPILE-b alone. The injection of the mixture of rCPILE-a and the trypsin-treated rCPILE-b into an ileum loop of rabbits evoked the swelling of the loop and accumulation of the fluid dose-dependently, suggesting that CPILE possesses enterotoxic activity. The evidence presented in this communication will facilitate the epidemiological, etiological, and toxicological studies of C. perfringens food poisoning, and also stimulate studies on the transfer of the toxins’ gene(s) among the Genus Clostridium.

An epidemiological review of gastrointestinal outbreaks associated withClostridium perfringens, North East of England, 2012–2014

An anecdotal increase inC. perfringensoutbreaks was observed in the North East of England during 2012–2014. We describe findings of investigations in order to further understanding of the epidemiology of these outbreaks and inform control measures. All culture-positive (>105c.f.u./g) outbreaks reported to the North East Health Protection Team from 1 January 2012 to 31 December 2014 were included. Epidemiological (attack rate, symptom profile and positive associations with a suspected vehicle of infection), environmental (deficiencies in food preparation or hygiene practices and suspected vehicle of infection) and microbiological investigations are described. Forty-six outbreaks were included (83% reported from care homes). Enterotoxin (cpe) gene-bearerC. perfringenswere detected by PCR in 20/46 (43%) and enterotoxin (by ELISA) and/or enterotoxigenic faecal/food isolates with indistinguishable molecular profiles in 12/46 (26%) outbreaks. Concerns about temperature control of foods were documented in 20/46 (43%) outbreaks. A suspected vehicle of infection was documented in 21/46 (46%) of outbreaks (meat-containing vehicle in 20/21). In 15/21 (71%) identification of the suspected vehicle was based on descriptive evidence alone, in 5/21 (24%) with supporting evidence from an epidemiological study and in 2/21 (10%) with supporting microbiological evidence.C. perfringens-associated illness is preventable and although identification of foodborne outbreaks is challenging, a risk mitigation approach should be taken, particularly in vulnerable populations such as care homes for the elderly.

A diagnosis of the microbiological quality of dehydrated bee-pollen produced in Brazil

Bee-pollen is an apicultural product with potential for medical and nutritional applications; therefore, its microbiology quality should be monitored. In this context, the objective of this study was to diagnose the microbiological quality of 45 dehydrated bee-pollen samples collected from November 2011 to December 2013 in nine Brazilian States. All the samples were negative for sulphite-reducing Clostridium spores, Salmonella, coagulase-positive Staphylococcus and Escherichia coli, which are micro-organisms of public health concern. Total aerobic mesophilic micro-organism counts ranged from <10 to 1·10 × 10(4) CFU g(-1) , with psychrotroph counts ranging from <10 to 1·12 × 10(3) CFU g(-1) and total coliforms from <10 to 2·80 × 10(3) CFU g(-1) , while the values for yeasts and moulds were between <10 to 7·67 × 10(3) CFU g(-1) . According to the literature, the microbiota observed in this study were typical; however, it is important to consider that these micro-organisms may cause spoilage and diminish shelf life, reason by which quality control programs should be implemented.

SIGNIFICANCE AND IMPACT OF THE STUDY

Contamination of bee-pollen can occur during production, collection and processing, but there are few studies of the microbiological quality of this product. Brazil is an important producer of dehydrated bee-pollen, therefore, a diagnosis of the microbiological status is important to ensure the safety of many consumers. Salmonella sp., genus Clostridium, coagulase-positive Staphylococcus, Escherichia coli and even some yeast species are micro-organisms of public health concern and their presence must be monitored. Furthermore, the determination of spoilage micro-organisms indicates whether the production and the processing practices carried out by beekeepers and warehouses were adequate.